The radiation pattern of the large parabolic reflectors
of the Transportable Atmospheric RAdar system (TARA), developed
at Delft University of Technology, has been accurately simulated.
The electric field integral equation (EFIE) formulation has
been applied to a model of the reflectors including the feed housing
and supporting struts, discretised using the method of moments.
Because the problem is electrically large (the reflector has a diameter
of 33λ) and nonsymmetrical, this lead to a badly conditioned
linear system of approximately half a million unknowns.
In order to solve this system, an iterative solver (generalized minimum
residual method) was used, in combination with the multilevel
fast multipole method. Because of the bad conditioning, the
system could only be solved by using a huge preconditioner. A new
block-incomplete LU preconditioner (ILU) algorithm has been employed
to allow for efficient out-of-computer core memory preconditioning.